allergy medication, over the counter

What is Diphenhydramine?

It is a first generation antihistamine, or allergy medication.  It is used for year round and seasonal allergies.   It treats the following symptoms: red itchy eyes, runny nose, sneezing, hives and more allergy related symptoms.

It may be listed as diphenhydramine hcl or diphenhydramine hydrochloride.

It is sold in the United States and Canada under the brand name Benadryl®, and is available in many stores brands too.

It is also used as a sleep aid, due to the most common side effect of  drowsiness.  As a sleep aid it is sold under the brand names: Simply Sleep®, Unisom® and Sominex®.

Side Effects

Drowsiness is the most common side effect.  Others include: low blood pressure, racing heart, faint or dizziness, dry mouth, nausea, constipation, weight gain and increase appetite and increased sensitivity to sunlight.

Many report unusual or vivid dreams.

Contact your doctor or pharmacist if you are concerned about side effects.

Do not use alcohol to reduce the risk of increased drowsiness


Adults can take diphenydramine 25 mg every 4 hours as needed, no more than six 25mg tablets per day.

Children 6 to 12 years old can use 12.5mg every 4 to 6 hours, max 6 doses per day

Children 2 to 6 years old (only use with Doctor’s recommendation) can use 6.25mg (usually 1/2 teaspoon) every 4 hours.  Max 4 doses per day

Use caution if taking diphenhydramine during the day, it can make you drowsy and slow your reaction time.

Avoid using with alcohol.


If you suspect an overdose call 911 or take the person to the doctor immediately.

Symptoms of an overdose include: drop in blood pressure, heart attack, slowed or stopped breathing, coma, confusion, seizure, anxiety, hyperactive, change in behavior, aggressiveness, fever and dilated pupils.


Diphenhydramine is consider a pregnancy category B.  Meaning it is probably safe, however, it does cross the placenta.  Talk with your health care provider before using.

It is excreted is breast milk.

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The pharmaceutical information on this site is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes. This information is not intended to be patient education and should not be used as a substitute for professional diagnosis and treatment.
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